Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $42.92   9.324%   $46.9219   $46.92   $46.90   $46.90  
  Purchase #2 $221.65   11.531%   $247.2085   $247.21   $247.20   $247.20  
  Purchase #3 $42.46   3.611%   $43.9932   $43.99   $44.00   $44.00  
  Purchase #4 $198.27   5.600%   $209.3731   $209.37   $209.35   $209.40  
  Purchase #5 $222.62   10.798%   $246.6585   $246.66   $246.65   $246.70  
  Purchase #6 $192.57   5.591%   $203.3366   $203.34   $203.35   $203.30  
  Purchase #7 $32.81   7.262%   $35.1927   $35.19   $35.20   $35.20  
  7 purchase totals = $953.30       $1,032.6845   $1,032.68   $1,032.65   $1,032.70